Overview

The goal of the Delphoi is provide adaptive components
to other modules of the Grid Application Toolkit (GAT).
Common to these adaptive components is that they take
(possibly dynamic) information about Grid resources
(network status, CPU availability, memory footprint, etc.) as
input to performance-prediction models and implement adaptive
strategies that let applications use the given resources more efficiently.
For grid-aware applications, this general mechanism is used for numerous
purposes like data access, task scheduling, and dynamic application
reconfiguration. Although use-case specific APIs and event models
are necessary, the basic techniques are similar.

In the Delphoi, we generalize the basic techniques of gathering relevant
monitoring data (e.g., provided by
Mercury)
and correlating this data with performance models to provide short-term
performance predictions.
These predictions can be used to adapt the behavior of applications,
or as input to other services
(e.g., GRMS).

Our place in the GridLab architecture:

This picture shows the main components of our information gathering software.
A large number of components (in the core layer) are distributed over the
testbed. These components, called Pythias, are responsable for gathering local
information. The Pythias locally store this information for later use.

The Delphoi is a centralized component in the service layer. Using a web
service interface, it allows the retrieval of historic data and short term
predictions from the Pythias. It also provides detailed performance related
data to several other services.